FIG. 1 is a schematic block diagram of communication systems comprising a terminal 2 equipment such as a host device and a modem 4. The host terminal 2 may be a user terminal, and may for example take the form of a desktop computer, laptop computer, tablet style computer, or mobile phone (which may be referred to as a “smart phone”). As shown in FIG. 1, the modem 4 may for example take the form of a dongle for plugging into the host terminal 2 such that the modem 4 is connected to a host processor 30 (otherwise referred to as an application processor) of the host terminal 2. Alternatively the modem 4 may take the form of a mobile phone handset which, as well as being a conventional mobile telephone, can be connected to the host terminal 2 so as to act as an external cellular modem for the host terminal 2. As shown in FIG. 1, the modem 4 is external to the host terminal 2 in that it is a separate unit housed in a separate casing, but which is connected or connectable to the host processor 30 of the host terminal 2 by means of a wired or wireless connection (as well as being removable or being able to be disconnected from the host terminal 2).
The system also comprises a network 6 such as a mobile cellular network 6 (3GPP network or other CDMA network). Elements of the network 6 are well known to those skilled in the art and are not discussed herein.
For connecting to the mobile cellular network 6, the modem 4 comprises a first interface which comprises a wireless transceiver, typically in the form of a radio frequency (RF) transceiver and an antenna 5. The first interface of the modem 4 connects via an antenna (not shown) of the mobile cellular network 6 enabling the modem 4 to establish a channel between itself and the mobile cellular network 6.
This channel referred to above may be referred to as a “context”. For example, if the mobile cellular network is a 3GPP network, then the connection between the modem 4 and a 3GPP network 6 may be called a PDP (Packet Data Protocol) context in 2G or 3G terminology, and an EPS (Evolved Packet System) bearer context in LTE (Long Term Evolution standards) terminology. The physical medium of the connection is typically a radio channel such as a 2G, 3G or LTE radio channel and the protocol that drives it may comprise a set of protocol layers as defined for example by 3GPP. The mobile cellular network 6 may be coupled to a further, packet-based network, preferably a wide area internetwork such as the Internet, by way of one or more gateway routers.
For connecting to the host processor 30 on the host terminal 2, the modem 4 comprises a second interface which could, for example, comprise a wired connection such as USB, or a short-range wireless transceiver such as an infrared connection or a radio frequency connection (e.g. Bluetooth).
In the terminology of the 3GPP (Third Generation Partnership Protocol), the host terminal 2 is referred to as terminal equipment (TE). The host processor is sometimes referred to as an application processor, and controls a user interface UI which interfaces with a user. The modem 4 has a processor which is referred to as a mobile termination (MT).
The modem 4 includes a subscriber identity module (SIM) 7. The SM 7 communicates with the modem processor via a UICC interface. A SIM application tool kit (STK) comprises a set of commands programmed into the SIM which enable the SIM to initiate actions from the SIM itself. The commands programmed into the SIM enable the SIM to initiate commands independently of the network and host processor.
A SIM initiates an action by generating a proactive STK indication to the modem processor.
In scenarios such as that illustrated in FIG. 1 where the modem is a separate device which needs to communicate with the host processor, a mechanism is needed to determine how to handle actions initiated by the SIM.